This invention relates generally to imaging systems capable of operation in multiple modalities, and more particularly to methods and systems for conducting a pencil-beam computed tomography (CT) scan in a multi-modality system.
Multi-modality imaging systems are capable of scanning using different modalities, such as, for example, positron emission tomography (PET), single positron emission tomography (SPECT), computed tomography (CT), static x-ray imaging, and dynamic (fluoroscopy) x-ray imaging. In a multi-modal system (also referred to as a multi-modality system), a portion of the same hardware is utilized to perform different scans (e.g., an image produced by SPECT is processed and displayed respectively, by the same computer and display, as an image produced by CT). However, the data acquisition systems (also referred to as an “imaging assembly”) are different. For example, on a CT/SPECT system, a radiation source and a radiation detector are used in combination to acquire CT data, while a radiopharmaceutical is typically employed in combination with a SPECT camera to acquire SPECT data.
CT imaging is typically performed using a relatively expensive x-ray source and x-ray detector. A relatively less expensive CT imaging system is a pencil-beam CT system wherein a relatively narrow, cylindrical beam of x-rays are directed towards a relatively inexpensive detector. A pencil-beam CT system architecture facilitates reducing x-ray scatter, producing a relatively high quality image. However, a scan using a pencil-beam CT system typically takes a longer amount of time than scans using typical CT systems. Specifically, emission scans, for example, PET and SPECT scans, typically take several minutes, for example, approximately twenty minutes, whereas a transmission scan, for example, a CT scan, typically takes only several seconds, for example, approximately fifteen seconds.